1. Field of the Invention
The present invention relates to a keyboard device for use with a musical instrument having a keyboard such as an electronic piano or the like.
2. Description of the Related Art
Conventionally, keyboard devices for keyboard-based musical instruments of the type mentioned above are known, for example, as described in Laid-open Japanese Patent Application No. 63-128397. The keyboard device disclosed therein has a large number of keys arranged in the left-to-right direction on a single chassis (frame) made of metal. The chassis is formed with a large number of grooves and holes such that the respective keys are pivotably attached to the chassis while they remain engaged with the grooves and holes associated therewith. The chassis is integrally fabricated by punching a single metal plate (for example, a steel plate) using a press tool and bending the punched metal plate using a bending tool.
Some keyboard devices employ a chassis made of a synthetic resin in place of a metal chassis. The synthetic resin chassis as mentioned may be injection molded by an injection molding machine comprising an injection molding tool.
The above-mentioned keyboard device has all keys carried on a single chassis, so that the chassis has a size larger than the width (the length in the left-to-right direction) of all the keys. This leads to requirements to larger manufacturing facilities including a press tool, a bending tool, a mold for injection molding, a press machine, an injection molding machine, and so on, all of which must be used during machining of the chassis, thereby resulting in an increased manufacturing cost. In addition, in a trial manufacturing stage, holes and key guides formed in the chassis may deviate from the positions at which they should be, due to manufacturing errors in tools and molds, in which case the tools and molds must be adjusted for correcting deviated positions, if any. In this event, as the tools and molds are large, positionally deviated grooves and holes must be adjusted over a wider range, thereby incurring a problem that the adjustments for the tools and molds require significant time and labor, and as a result the manufacturing cost is further increased.
Generally, keyboard devices are not limited to normal ones having 88 keys but may have a variety of numbers of keys. For this reason, tools and molds, if fabricated for machining a chassis for a keyboard device having 88 keys, by way of example, cannot be diverted to the machining of a chassis for a keyboard device having 76 keys. Consequently, various kinds of tools and molds must be individually fabricated in order to manufacture a variety of chassis for musical instruments having different numbers of keys, thereby causing a further increase in the manufacturing cost.